Task/570 type not exist

### Description
Two new URI parameters:
  - !exist='entity::type'
  - exist='entity::type'

The info can also be passed as a scope in requests that have restriction.
For this, a new field for the operation-scope in the input payload has been invented:
XML:

    <scope>
      <operationScope>
        <scopeOperator>not</scopeOperator>
      </operationScope>
    </scope>

JSON:
  "scopes": [
    {
      "operator": "not"
    }

It is a little bit strange as rest/uriParamNames.h will have to include ngsi/Scope.h.
But it is better than the other way around, I guess.